The invention relates to a parts feeder according to the preamble of claim 1.
For the transfer of parts, which are supplied in the form of bulk goods in a storage container, to a robot, the parts as a rule firstly have to be separated from one another (that is to say individualized) and brought into an orientation and position suitable for the transfer to the robot. This task is carried out by parts feeders, as they are known (also referred to as feed systems). A parts feeder accordingly picks up parts in the form of bulk goods, separates the parts and transfers them in a suitable orientation and position to a robot. The robot grips the suitably oriented parts in a selection zone of the parts feeder and subsequently transfers them for further processing and/or mounting to a mounting system, a processing station or the like. In this connection, a robot is to be understood as any kind of apparatus for gripping parts in a favorable orientation and position and subsequently conveying them away from the point at which they are gripped or selected.
Most customary parts feeders comprise a mechanical filter in the form of a vibrating pot which can be rotated about a vertical axis to separate the parts and to orient and position the same. The pot is provided with internal, spiral volutes. Arranged along the volutes are a large number of mechanical guide elements and barriers. On account of the vibrating rotational movement of the pot, the parts are transported upward along the volutes to the outlet of the pot. By means of the barriers and guide elements, only parts in a specific orientation are transported as far as the outlet of the pot, the remainder fall back onto the bottom of the pot in order to begin a renewed transport operation along the volutes. From the outlet of the pot, the parts are typically conveyed onward via linear rails, in order to maintain their separation and orientation.
The mechanical filters in the form of vibrating pots have the disadvantage that they are tailored specifically to specific parts. They are extremely inflexible in relation to changes in the parts. In the event of a modification to the geometric form of the parts, most often the entire vibrating pot has to be redesigned, constructed and tested. In addition, both the volutes of vibrating pots and the linear rails adjacent to the pots are susceptible to blockages as a result of defective and/or particularly unfavorably positioned parts, in particular when the latter have a complicated geometric form.
In the U.S. Pat. No. 5,687,831 (Adept Technology), a parts feeder is described which, as compared with vibrating pots, exhibits improved flexibility in relation to different parts forms. The parts feeder according to U.S. Pat. No. 5,687,831 comprises an essentially horizontal transport section on which the parts are transported to a selection zone. In the selection zone, favorably oriented and arranged parts are detected by means of a video camera and are subsequently gripped by a robot and transferred to a mounting system. The parts that are not selected are guided back to the start of the transport section by means of a recirculation system for a renewed passage through the parts feeder. While they are being fed back, the orientation and the position of the parts are changed in order that they may be oriented favorably during the next pass and selected in the selection zone.
Although the parts feeder according to U.S. Pat. No. 5,687,831 is to a certain extent flexible in relation to different parts forms, it is relatively complicated in design terms and requires a considerable amount of space for the arrangement of the transport section, the selection zone and the recirculation system.
It is an object of the present invention to provide a parts feeder which is simple in design terms, space-saving and flexible in relation to different parts forms.
The object is achieved as defined by the features of the independent patent claims.
According to the invention, a parts feeder for a robot has a selection zone accessible to the robot, a device for changing the orientation and/or the position of the parts stochastically, and a device with a parts recirculation element for recirculating the parts. The device for changing the orientation and/or the position of the parts stochastically is a vibrating platform constructed at the same time as a selection zone. The parts recirculation element and the vibrating platform can be brought relative to each other into two different positions in such a way that in the first position the vibrating platform can be loaded with parts from the parts recirculation element and in the second position the parts which fall down from the vibrating platform can be collected by the parts recirculation element.
In the course of the present description and the claims, a parts recirculation element is always to be understood as an element provided to recirculate parts. Such a parts recirculation element can be constructed, for example, as a separate section, as a zone or parts carrying area which can be moved with respect to the vibrating platform, as a recirculation container constructed so as to accommodate a few parts, or as a storage container constructed so as to accommodate a large quantity of parts.
The parts recirculation element is used firstly, in a first position, to load the vibrating platform with parts. As soon as the vibrating platform has been loaded with a sufficient number of parts, the parts recirculation element and the vibrating platform are brought relative to each other into a second position, in which the same parts recirculation element is used to collect parts which fall down from the vibrating platform during the vibration. At the same time, the vibrating platform serves as a selection zone for the parts feeder, that is to say the parts are gripped by the robot on the vibrating platform and conveyed away. (The actions of gripping the parts and conveying them away is also referred to as selecting the parts.) If the number of parts remaining on the vibrating platform falls below a minimum number, the parts recirculation element and the vibrating platform are brought relative to each other into the first position again, in order to load the vibrating platform again with parts from the parts recirculation element. As a result, the parts which have fallen down from the vibrating platform onto or into the parts recirculation element are guided back to the vibrating platform and are therefore recycled. The parts recirculation element therefore serves alternately as a parts reservoir for loading the vibrating platform with parts and as a collecting element for collecting the parts that fall down from the vibrating platform, in order subsequently to recycle the latter. Because the same element is used to load the vibrating platform with parts and to collect the parts falling down from the vibrating platform, the necessity for separate parts transport devices to feed back the parts that have fallen down from the vibrating platform, and their renewed feeding to the vibrating platform are dispensed with. As opposed to previously known parts feeders, the parts feeder according to the invention therefore manages without any parts transport devices for horizontal parts conveyance, such as conveyor belts, linear rails or the like. This permits an extremely simple and space-saving construction of the parts feeder according to the invention. In addition, as a result of the elimination of the conveyor belts and linear rails, which are susceptible to blockage, the risk of blockage of the entire parts feeder can be reduced substantially.
The vibrating platform and the parts recirculation element can be moved relative to each other. In order to produce the relative movement, either the vibrating platform can be arranged to be substantially fixed to a frame of the parts feeder, and the parts recirculation element can be arranged to be movable with respect to this frame and therefore to the vibrating platform. Or, vice versa, the parts recirculation element can be arranged to be fixed to the frame of the parts feeder and the vibrating platform can be arranged to be movable on the frame. It goes without saying that, in principle, both the parts recirculation element and the vibrating platform can be arranged to be movable on the frame of the parts feeder, in order to provide relative movement between the parts recirculation element and the vibrating platform.
The parts recirculation element can be designed like a trough, that is to say as a container open at the top and having a bottom and side walls, in order to assist the collection of the parts in the second position. The parts can then simply fall down from above into the trough-like parts recirculation element.
The parts recirculation element is preferably provided with an interchangeable upper part, the upper side of this upper part being adapted to a desired number of parts which, in the first position of the parts recirculation element, are conveyed from the parts recirculation element to the vibrating platform in order to load the vibrating platform.
According to a preferred embodiment of the invention, the parts recirculation element is arranged in the immediate vicinity of the vibrating platform and can be displaced in the manner of a lift in the vertical direction between the first position for loading the vibrating platform and the second position for collecting the parts. In the first, raised position, the parts recirculation element is arranged at a level that is increased with respect to the vibrating platform in such a way that the parts are conveyed from the parts recirculation element to the vibrating platform substantially by the force of gravity. In the second, lowered position, the parts recirculation element is arranged at a level that is lower with respect to the vibrating platform in such a way that the parts that fall down from the vibrating platform as a result of the vibration of the latter fall onto or into the parts recirculation element substantially on account of the force of gravity. In order to load the vibrating platform with parts, a parts recirculation element of trough-like design can be provided with a lateral outlet opening. As an alternative, a parts recirculation element can also be designed like a funnel, the vibrating platform being arranged at the center of the funnel-like parts recirculation element. It is preferable for the bottom of the parts recirculation element, carrying the parts, to be inclined downward toward the vibrating platform so that the parts flow toward the vibrating platform merely on account of the force of gravity. This represents an extremely simple possible way of conveying parts within the parts recirculation element.
In a parts feeder for a robot, having a selection zone accessible to the robot, and a device for changing the orientation and/or the position of the parts stochastically, the device for changing the orientation and/or the position of the parts stochastically can be a vibrating platform constructed at the same time as a selection zone, the vibrating platform being constructed to execute vibrating movements with a single mechanical degree of freedom. In this case, the number of degrees of freedom is, as usual, understood to mean the number of mutually independent determinants (coordinates) which are needed in order to determine the system uniquely. For example, a mass point that can move freely in space has three mechanical degrees of freedom, while a mass point that moves on a curve has one degree of freedom. Since, in the case of a parts feeder according to this variant of the invention, the entire vibrating platform has to be moved simply with a single mechanical degree of freedom, the vibrating platform itself, the drive for producing the vibrating movement us [sic] therefore the entire parts feeder can be constructed extremely simply and cost-effectively. For example, a cost-effective, simple vibrating device can be used for the drive of the vibrating platform, as is common for constructional machines. It is clear that this aspect of the invention does not necessarily have to be used in connection with the parts recirculation element that can be moved with respect to the vibrating platform in order to recirculate the parts.
The vibrating platform that can be moved with a single mechanical degree of freedom is preferably constructed to execute vibrating movements substantially in the vertical direction, so that the vibrations or the vibrating movements are carried out only in the vertical direction. As opposed to previous parts feeders, the parts are then not specifically conveyed in a horizontal direction by the vibrating platform. The vibrating platform merely has the function of separating the parts by throwing the latter repeatedly upward and of changing their orientation and their position stochastically. In addition, it is advantageous if the vibrating platform is provided with a drive device for generating the vibrating movement, which permits optional setting of the frequency, the amplitude and the duration of the vibrating movement. The frequency, the amplitude and the duration of the vibrating movement can in particular be set by software in order to provide a programmable control device to control the vibrating platform. By setting the frequency, the amplitude and the duration of the vibrating movement, the parts feeder can be adapted in a simple way to different parts forms. Before processing parts with a new form, these parameters can be optimized, in a setting or test phase, for the greatest possible efficiency with regard to the desired orientation and/or position of the parts to be processed.
The vibrating platform of a parts feeder according to the invention can also be provided with an interchangeable supporting surface on the upper side of the platform, it being possible for the supporting surface (xe2x80x9ctooling platexe2x80x9d), on which the parts come to lie, to be structured and to be adapted to specific parts forms and/or specific parts ranges. This provides the possibility of arranging the parts, by means of stochastic vibration, in an orientation whose probability of occurrence is comparatively low. In this way, for example, parts can be arranged to stand on their narrow side. In addition to the abovementioned settable parameters of the vibrating movement, the interchangeable supporting surface permits further simple possible adaptation of the parts feeder to different parts forms, by the supporting surface being able to be interchanged for a new parts form and replaced by a supporting surface adapted to the new parts form.
According to a further preferred embodiment of the invention, the parts feeder further comprises a detection device for detecting the orientation and the position of the parts on the vibrating platform, and also data transmission means for transmitting the detected orientations and positions to the robot, in order to assist the selection of the parts by the robot on the vibrating platform, serving at the same time as a selection zone. The detection device preferably comprises means for optical orientation and position detection and also means for illuminating the vibrating platform, the optical detection means and the illumination means being arranged in a common housing. The housing can be provided with a viewing opening aimed at the platform, the housing preferably being simply open in the direction of the platform, in order to prevent disruption caused by the influence of external light. Furthermore, the housing can be movable over the vibrating platform, in order to detect the orientation and the position of the parts. For this purpose, the housing can be arranged on a substantially horizontal running rail arranged above the vibrating platform. By means of the camera, which can be moved over the vibrating platform together with the illumination means in a housing, the parts feeder becomes independent of the robot to which it feeds the parts. In the case of a parts feeder with a stationary camera and a robot which moves in the visible area between the camera and the selection zone, this is not so.
According to a method according to the invention for operating a parts feeder for a robot, the following steps are carried out one after another in a continuous endless procedure: in a first step, a vibrating platform constructed so as to change the orientation and/or the position of the parts stochastically by vibrating, and a parts recirculation element, are moved relative to each other into a first position, the vibrating platform then being loaded with parts from the parts recirculation element in this first position. In a second step, the vibrating platform and the parts recirculation element are moved relative to each other into a second position to collect parts which fall down from the vibrating platform. The parts are collected in or on this parts recirculation element. In a third step, the orientation and/or the position of the parts on the vibrating platform is/are changed stochastically by vibrating the vibrating platform, any parts that fall down from the vibrating platform being collected by the parts recirculation element. In a fourth step, the orientation and the position of the parts on the vibrating platform are detected, and the corresponding orientation and position data are transmitted to the robot. In a fifth step, depending on the transmitted orientation and position data of the parts, any parts with a favorable orientation and position are gripped by the robot on the vibrating platform, serving at the same time as a selection zone, and are conveyed away, that is to say selected. In a sixth step, the number of parts remaining on the vibrating platform is determined, a return then being made either to the third step or to the first step, depending on this number. If the number of parts remaining on the vibrating platform is lower than a predefined minimum number, then a return is made to the first step, otherwise to the third step.
In a variant of the method, instead of the control by the sixth step, the return to the first step can be controlled by the expiry of a predefined time since the last execution of the first step. In another variant, this return to the first step can be controlled by the area coverage of the vibrating platform.
In the case of a parts recirculation element designed like a trough, the method can further comprise a seventh step, which is executed after the sixth step before the return to the first step, the number of parts in the parts recirculation element being determined in this seventh step and the parts recirculation element being filled with new parts on the basis of this number. As an alternative to putting the new parts into the trough-like parts recirculation element, the new parts can also be conveyed directly onto the vibrating platform by an additional conveying device.
The method according to the invention for the operation of a parts feeder for a robot is preferably carried out completely automatically, so that no manipulations by hand are necessary.